Smith, who supported Trident renewal, says he is on the left of the party, and is also a former BBC journalist.

Here are 15 facts to know about the leadership contender as the race heats up:

1He used to be a BBC producer

Nick Ansell/PA Wire

Smith was a BBC radio producer for a decade, joining BBC Wales in 1992 - the same year his father also became editor of BBC Wales. "Colleagues recall an amiable but highly ambitious character," one BBC profile claims. His jobs included work on the flagship Radio 4 programme Today and the politics programme Dragon's Eye which broadcasts in Wales.

2The Met Police complained about him

Hemera Technologies via Getty Images

When working as a young man on Today, he prompted a complaint by the Met Police after calling a police emergency hotline, rather than the press office, to ask for updates on a story. Smith told the BBC's Victoria Derbyshire programme that the move was "pretty stupid", adding: "I was embarrassed about it at the time, I am embarrassed about it now, but I think my judgement isn't called into question by this, it was a foolish mistake a young man."

3He joined Labour aged 16

Matthew Horwood via Getty Images

He was born in Lancashire, in 1970, and his father is the Welsh historian Dai Smith.

4He is "on the left" of the party

Matthew Horwood via Getty Images

Smith himself as “on the left" of Labour, saying he agrees with many of Jeremy Corbyn's views but wants to"modernize" some of the values the current leader holds.

5He was a lobbyist for big pharma

Mark Lennihan/AP

Before becoming an MP in 2010, Smith worked for pharmaceuticals giant Pfizer, becoming head of policy and government relations. He later joined another pharma company, Amgen.

On Wednesday he was forced to defend himself against claims he backs NHS privatisation, after he said “choice is a good thing” on behalf of Pfizer in 2005. Smith said the accusations were Speaking to BBC Radio 4’s today programme said it was “clearly not true" and that he has "never advocated privatization of the NHS."

6He hasn't used Viagra

Creative Crop via Getty Images

After Piers Morgan asked Smith whether he tried Viagra in his role at Pfizer, he replied: “No, I haven’t actually, I haven’t needed it.” Asked if he tried any products from the company, he joked: "That’s for me and Mrs Smith to know about."

7He would have voted against the Iraq war

Andrew Matthews/PA Wire

Smith only became an MP in 2010, so didn't vote on the UK going to war with Iraq. He has said he would have voted against the war and been "opposed to it at the time".

Smith's voting record show he has almost always voted against reducing housing benefit for social tenants deemed to have excess bedrooms, and has consistently voted for raising welfare benefits. His votes on the Uk's role in the EU have been mixed. Read his full voting record here.

10Nye Bevan is one of his heroes

PA/PA Archive

Aneurin Bevan, known as Nye, was a Welsh Labour politician that Smith has quoted and cited as an inspiration. Bevan was regarded as a leading spokesperson for the Left and was Minister for Health under Attlee, credited with spearheading the establishment of the NHS.

11He gets compared to Tony Blair a lot

ASSOCIATED PRESS

Smith has been accused of being the 'Blairite-lite' candidate by Corbyn's team, while the BBC reported his press conference to launch his bid “could have come straight from the Cameron/Blair playbook” because he wore a white shirt with no tie and appeared surrounded by his family and "a youthful band of supporters".

12He wants to change the Labour constitution

PA/PA Archive

One of his flagship policies is to rewrite Clause IV of the Labour constitution, to include a specific commitment to fight inequality.

13He supported Trident renewal

Mark McLaughlin/PA Wire

Unlike Jeremy Corbyn, Smith was one of the MPs backing plans to renew the UK's nuclear deterrent, which were voted in on Monday.

14He marched with striking miners

Gareth Fuller/PA Wire

He called the 1984 miner’s strike his “political awakening” when he launched his leadership bid, and said he had marched with miners from the Maerdy Colliery. He told the audience in his constituency he was inspired by their "sense of community, solidarity and passion for justice".

15He is proudly Welsh

Matthew Horwood via Getty Images

Despite being born in Morecambe, Lancashire, Smith grew up in South Wales. His father Dai is a former chairman of the Arts Council of Wales as well as a historian, described by The Guardian as being "dead centre of the 'Taffia'" - at the heart of Welsh politics and media.